call/apply/bind

apply.js

/**
 * 手动实现apply方法
 *
 */
function fakeApply(context, arr) {
    context.applyFn = this;
    var args = [];
    for (var i = 0; arr && i < arr.length; i++) {
        args.push('arr[' + i + ']');
    }
    var result = eval('context.applyFn('+ args +')');
    delete context.applyFn;
    return result;
}
if (!Function.prototype.apply) {
    Function.prototype.apply = fakeApply;
}
Function.prototype.fakeApply = fakeApply;

bind.js

/**
 * 手动实现bind方法
 *
 */
function fakeBind(context) {
    var fn = this;
    var args = [];
    var preArgs = [];
    for (var i = 1; i < arguments.length; i++) {
        preArgs.push(arguments[i]);
        args.push('preArgs[' + (i - 1) + ']');
    }
    return function () {
      for (var i = 0; i < arguments.length; i++) {
        args.push('arguments[' + i + ']');
      }
      context.bindFn = fn;
      var result = eval('context.bindFn(' + args + ')');
      delete context.bindFn;
    };
}
if (!Function.prototype.bind) {
    Function.prototype.bind = fakeBind;
}
Function.prototype.fakeBind = fakeBind;

call.js

/**
 * 手动实现call方法
 *
 */
function fakeCall(context) {
    context.callFn = this;
    var agrs = [];
    for (var i = 1; i < arguments.length; i++) {
        agrs.push('arguments['+ i +']');
    }
    var result = eval('context.callFn(' + agrs + ')');
    delete context.callFn;
    return result;
}
if (!Function.prototype.call) {
    Function.prototype.call = fakeCall;
}
Function.prototype.fakeCall = fakeCall;